Reversible fan



- June 2 5 1940- K. D. McMAHAN REVERSIBLE FAN Filed Aug. 12. 1937 Inventor Kenton D. McMahan,

His ttorrley Patented June 25, I940 UNITED STATES REVERSIBLE FAN .Kenton D. McMahan,

Schenectady, N. Y., as-

signor to General Electric Company, 'a corporation of New York Application August 12, 1937,- Serial No. 158,690

12 Claims.

The present invention relates to reversible centrifugal fans.

In centrifugal fans the air is discharged radially from the blades into a passage called a scroll 5 which increases in area around the fan in its direction of rotation toward the outlet. A scroll designed for eflicientoperation with one direction of fan rotation will have a-very low efficiency when the fan is operated in the reverse direction m: of rotation.

The object of my invention is to provide an improved construction and arrangement in casings for-centrifugal fans in which the shape of scroll may be readily altered in accordance with u the direction of rotation of the fan to produce eflicient operation in both directions of rotation. For a considerationof what I believe to be novel and my invention, attention is directed to the accompanying description and the claims appended thereto. v

' In the accompanying drawing, Figure 1 is a sectional end elevation of a centrifugal fan embodying my invention, the parts being in the position for counterclockwise rotation of the fan; and Figure 2 is a view similar to Figure 1, the parts being in the position for clockwise rotation of the fan. a

Referring to the drawing, the fan housing oomprises spaced end walls I, only one ofwhich is 9 shown, which are connected around their edges by peripheral walls 2. The walls 2 are symmetrical about a vertical axis extending through the center of the fan casing. Extending transversely between the walls I at the upper end of the fan casing is wall 3 which divides the casing into outlet passages 4 and 5. Within. the casing is a fan 6 which comprises blades 1 connected at one end to a ring .8 and at the other end to disk 9. The disk 9 is fixed to a hub ID, in turn fixed 40 to a drive shaft ll. During the operation of the fan air is admitted axially to the inner ends l2 of the blades through an inlet opening (not shown) and is discharged radially from the outer ends l3 of the blades. The walls I and 2 of the fan casing provide a passage around the fan into which the fan discharges, the passage leading to outlets 4 and 5; The shape of this passage is not suited for eflicient operation of the fan in either direction. 'Qxtending transversely 2 is a flexible wall I4 which may be made of suitable material, for example, a band of spring steel. Being located wholly within the passage defined by the casing walls, leakage between the 55 edges of the wall l4 and the walls I is not imbetween the walls I within the peripheral walls portant and packing is not required. Of course if such packing .were supplied, the outer wall 2, would be eliminated. The midpoint of the wall 14 is hinged at I5 to the fan casing. The ends of theband are pivoted to lugs l6 and I! which are fixed to a controlfrod l8 slidably carried in a bearing IS in the wall 3. Upon reciprocation of the control rod, the flexible wall I4 is moved transversely to its face laterally or radially toward and away from the fan. The right end of the rod l8 slidably projects outside the fan casing through a bearing 20 in the wall 2 and the projecting end of the rod is provided with a handle 2|. When the rod is in the position shown in Figure 2, the left end of the rod fits in a socket 22 in the wall 2. v I

x The contour of the flexible wall I4 is determined by stops, such as pins 23 and 24 carried by walls I, which respectively engage the inner and outer surfaces of the band in accordance .with the position of the rod l8. When the rod I8 is in the position shown in Figure 1 the outer surfaces of the portion of the wall l4 to. the right of the pivot l5 engages the pins 24 and the inner surface of the portion of the wall to the left of the pivot l5 engages the pins 23. The left end of the wall I4 is adjacent the edge .25 of a cutoif 26 integral with the wall 3. The pins 23 .and24 are so located thatthe wall l4 provides a scroll or'passage around the fan blades which gradually increases in area. from the cutoff 26 around the jail in a counterclockwise direction toward the/outlet 4. In this position the fan will operate efliciently when rotated in a counterclockwise direction. and will discharge air through the outlet-4. The edge 21 of the out off 26 provides a dam directing the air to the outlet 4. The upper surface 28 of the edge 21 is inclined toward the wall 3 to assist in directing the air through the outlet 4.

' When the control rod I8 is in the position shown in Figure 2 the inner surface of the portion of the wall l4 to the right of the pivot I 5 engages the pins 23 and the outer surface of the portion of the wall to-the left of the pivot l5 engages the pins 24. Inthis position the right end of the wall I4 is adjacent the edge 21 of the cutoff 26 and the left end of the wall is adjacent the wall 2 of the casing. The wall I4 now provides a scroll or passage around the fan blades which increases in area from the cutoif 26 aroundthe'fan in a clockwise direction toward the outlet 5. In this-position the fan will operate efiiciently when rotated in a clockwise direction and will discharge air through the outlet 5. The edge 25 of the cutoff serves as a dam directing air to the outlet 5, the upper surface 29 thereof being in-' clined toward the wall 3 to assist in directing the air. e. V

The use of a flexible band 'or wall for changing the shape of the scroll in accordance with the direction of rotation of the fan permits a more efficient scroll since the band is free to What I claim as new and desire to secure by Letters Patent of the United States is:

- 1. In a reversible centrifugal fan, a fan casing having a wall defining a passage around and spaced from the fan into which the fan discharges, said passage leading to an outlet, flexible walls at all times within said casing walls for changing the area of said passage, means engaging a portion of said flexible walls for moving the flexible walls transverse to the faces thereof, and stops engaging other portions of the flexible walls for determining the position thereof whereby said passage increases in area around the fan toward the outlet in the direction of rotation of the fan.

2. 'In a reversible centrifugal fan, a fan'casing having spaced end walls and a connecting peripheral wall defining a passage around and spaced from the periphery of the fan into which the fan discharges; said passage leading to an outlet, a flexible wall within the casing walls extending transversely across said spaced'walls, means pivoting said flexible wall on the casing intermediate its ends, means engaging the ends of said flexible walls for moving the walls toward and away from the periphery of the fan,

and stops engaging an intermediate portion of the flexible walls for limiting the movenient thereof whereby the passage increasesin area around the fan toward, the outlet in the direction of rotation of the fan.

3. In a reversible centrifugal fan, a fan casing having spaced end walls and a connecting peripheral wall defining a passage around the fan into whichthe fan discharges, a cut-off intermediate the ends of said peripheral wall defining therewith a'pair of outlets, walls within said casing walls on each side of said cut-01f movable transversely to the faces thereof toward and away from said cut-off to change the area of said passage whereby the passage increases in area around the fan toward one of said outlets in the direction of rotation of the fan.

.4. In a reversible centrifugal fan, a fan casing having spaced end walls and a connecting peripheral wall defining a passage around the fan into which the fan discharges, said passage leading to an outlet, a flexible wall within the casing wallsextending transversely across said spaced walls and movable toward and away from the fan to change the area of said passage, means pivoting said flexible wall on said casing intermediate its ends, means engaging the ends of said flexible wall for moving the wall to change the area of said passage, and stops engaging intermediate portions of said wall for limiting the movement thereof.

, 5. In a reversble centrifugal fan, a fan casing having spaced end walls-and a connecting peripheral wall defining a passage around the fan into which the fan discharges, a cut-off intermediate the ends of said peripheral wall defining therewith a pair of outlets, a flexible wall ex- 'mediate the ends of said peripheral wall defining therewith a pair of outlets, a flexible wall extending transversely between said end walls for varying the area of said passage, the ends thereof being on opposite sides of said cut-oil and being movable transverse'to the face of said wall toward and away from said cut-ofi, and stops engaging an intermediate portion of said flexible wall for limiting the movement thereof whereby said passage increases in area around the fan toward the outlet in the direction of rotation of the fan.

7. In a reversible centrifugal fan, a fan casing having spaced end walls and a connecting peripheral wall defining a passage around the fan into which the fan discharges, a cut off intermediate the ends of said peripheral wall defining therewith a pair of outlets, a flexible wall extending transversely between said end walls for varying the area'of said passage, the ends thereof being on opposite sides of. said cut-off and being movable toward and away from said cutoff, means pivoting the flexible wall on said casing intermediate its ends, and control means connected to the ends of the flexible wall for moving said ends toward and away from said cut-cit".

8. Ina reversible centrifugal fan, a fan casing having walls defining a passage around the fan into which the fan discharges, a cutoff in said passage having faces defining a pair of discharge passages, movable walls in said passages facing the cutoff and movable toward and away fromcharges, means for mounting the movable walls for shifting movement wholly within the casing walls and relative to the casing and to the impeller blades between positions corresponding to the direction of rotation of the impeller whereby, the passage increases in area around the impeller'toward the outlet in the direction of rotation of the impeller, and means for moving said movable walls.

10. In a reversible cehtrifugalian, a bladed centrifugal impeller, a casing having walls around and spaced from the impeller defining a passage to which the impeller discharges, said passage leading to an outlet, flexible walls wholly within said casing walls and movable therein by flexing transverse to the faces thereof to change the area of said passage, and means for flexing said wallsto positions in which said pas- Sage increases in area around the impeller in the direction-of rotation toward the outlet.

11. In 'a reversible centrifugal fan, a bladed centrifugal-impeller, a casing, movable walls cooperating with the casing walls to provide a passage around the impeller and spaced therefrom to which the impeller discharges, said passage leading to an outlet, and means for moving said movable walls transversely to the face thereof to change the area of said passage whereby the passage increases in area around the impeller in its direction of rotation toward the outlet.

v 12. In a reversible centrifugal tan, a bladed men n. MCMAHAN. 

